6/3-2

General

Well 6/3-2 was drilled on the gamma structure on an early Permian formed fault block, 1.4 km from the Norwegian/UK median line. The primary objective was to test Jurassic/Triassic sandstones at different levels for possible hydrocarbon accumulations. Secondary objectives were to test Cretaceous porous/fractured limestone/chalk and Rotliegend sandstone. The prognosed TD was 4325 m. The location was chosen due to the proximity to mature source rocks and oil/gas discoveries in British waters. Seismic anomalies indicated shallow gas. Due to this the original planned well location was abandoned and a new location was chosen 500 m to the east.

Operations and results

Wildcat well 6/3-2 was spudded with the semi-submersible installation ROSS Isle 21 November 1985 and drilled to TD at 4091 m in the Early Permian Rotliegend Formation. Some hole problems were experienced in the top of the 12 1/4" hole section. 9 5/8" casing was set close to the Zechstein formation before drilling the 8 1/2" hole into the salt. At 3772 m, an over-pressured zone of dolomite/slate was encountered. It was anticipated that one had found a "floating lens" enclosed in the evaporites. The well started flowing and pressure was increased to 2.05 g/cc in order to stabilise the well. Because of this a 7" liner had to be set in the middle of the salt. A 6" hole was drilled to base of the Zechstein Formation and a 5" liner was set in order to be able to reduce mud weight through the Rotliegend sandstone. The well was drilled with seawater/hi-vis pills/pre-hydrated bentonite through the top sections to 622 m, with gypsum/polymer mud from 622 m to top of the salt at 3400 m, and with Safemul oil based mud from 3400 m to TD. No indication of shallow gas was encountered at this location.

Top Cretaceous came in at 2511 m. There were some shows in the Cretaceous limestone/chalk. However, logs, cores and cuttings showed that the re